Air-cooled internal combustion engines and cylinder therefor



y 1957 F. A. E. PORSCHE ET AL 2,799,261

AIR-COOLED INTERNAL COMBUSTION ENGINES AND CYLINDER THEREFOR Filed Jan. 21, 1955 FIG-7 4EEJM, F +M AlR-COOLED INTERNAL COMBUSTION ENGINES AND CYLINDER'IHEREFOR Ferdinand A. E. Porsche, Stuttgart, and Egon Forstner, Stuttgart-Degerloch, Germany, assignors to Dr. Ing. h. c. F. Porsche K.-G., Stuttgart-Zulfenhauscn, Germany This invention relates to improvements inair-cooled internal combustion engines and more particularly to an improved cylinder construction therefor, in which the cooling air impelled by an ejector action of the exhaust gases of the cylinder are guided thereover by an air-guiding casing.

V The principal object of the invention is to provide a simple and inexpensive means for air cooling the engine.

Another object of the invention is to provide a C011. struction in which the exhaust gases of the cylinder are used to impel the cooling'air in such a manner as to not only cool the hottest parts of the cylinder but also to cool the injection nozzle or spark plug without the necessity .of providing special air guiding means and without changing the direction of flow of the cooling air over the cylinder.

In accordance with the invention, the foregoing objects are achieved by providing a. construction in which the cylinder is unjacketed or left open at least on one sidevfor the unrestricted access and inflow of air. In this construction the injection nozzle or spark plug, as the case may be, is disposed on. the. open or unjacketed part of the cylinder so that it is directly exposed to the incoming air stream aspirated by the exhaust gases of the cylinder. Furthermore, according to a. preferred construction, the ejector nozzle is located opposite the injection nozzle or spark plug and disposed insuch a manner that the exhaust gases discharged through the ejector nozzle aspirate the cooling air over the cylinder head substantially without change. of direction.

As a result of the foregoing construction the fuel injection nozzle or spark plug, as the case may be, is swept by the unheated stream of cooling air aspirated by the ejector nozzle. By disposing the ejector nozzle of the cylinder on the side opposite that of the fuel injection nozzle or spark plug, not only is a really effective cooling action effected over the entirecylinden'but it is also possible. to guide the stream'of cooling air insubstantially an unchanged direction or straight line of flow.

In the improved construction, the fuel injector nozzle, or its intakeconduit, is preferably integrally formed with the cylinder head, thereby simplifying the production and assembly of the engine and eliminating the presence of flanges and screws which are liable to 'set up eddies in the air flow over the cylinder. The exhaust gas conduit is also advantageously integrally formed with the cylinder head of the engine and extends from the cylinder head to the ejector nozzle. This construction is particularly useful and important when the direction of outward flow of the cooling air is not coextensive with its linear direction of flow over the cylinder head of the engine.

Effective cooling of the cylinder including the cylinder head, as described above, is achieved by providing air guiding casing sections at the air intake side of the cylinder so as to leave an opening or gap for the inflow of air, the width of which for the cylinder head is such that the cooling ribs on the cylinder head are not covered over or not substantially covered on the incoming side,

whereas the gap for the cylinder proper is somewhat narrower so that the side casing sections extend partly over the cooling ribs of the cylinder. On the ejector nozzleside of the cylinder and cylinder head the air guiding casing sections merge into a restricted flow duct or mixing pipe surrounding the nozzle to form an ejector.

The invention is described more in detail hereinafter in connection with the accompanying drawings which show, by way of example, one form of embodiment of the invention applied to a one-cylinder Diesel air-cooled internal combustion engine.

In the drawings:

Fig. l. is a side View of the internal combustion engine partly in vertical section, with parts not pertinent for the understanding oftheinvention broken away;

Fig. 2 is. a front view of the cylinder ofthe engine shown in Fig. 1; and r Fig. 3 is a horizontal sectionalview taken on the line III-III of Fig. l.

Referring to the drawings, the internal combustion engine shown therein comprises a cylinder 1 formed with horizontal cooling ribs 2,. a cylinder head 3 formedwith vertical cooling ribs .4 and 5 and horizontal cooling ribs 6' and 7.. The coolingrib 4 and 5 on the top of the cylinder head extend in the same direction, from front to rear. A sleeve 8 and a hood 9 are mounted on the cylinder head for housing the control mechanisms for the engine. A crankcase 10 is. attached to the lower face of the cylinder 1. An. injection nozzle 11 is disposed on the cylinder head and extends in a direction represented by the arrow R which also represents the direction of flow of the coolingair. The injection nozzle 11 is connected into an injection. conduit 11' in the cylinder head, the walls of which extend in the direction of. the arrow R. An exhaust gas conduit 12 is provided on the opposite side of the cylinder head from and in line with the injection nozzle,.the conduit 12 merging into an exhaust nozzle.13 having an exterior taper.

The cylinder head 3 is an integral casting including. the injection inlet conduit. 11', the exhaust conduit 12 and the exhaust nozzle 13,. thereby providing. a simplified construction, which incidentally, does away with the otherwise required flanges and screws which. would obstruct the flow of cooling air andcreate eddies in the air flow.

The cooling air is guided over the cylinder 1 and. the cylinder head 3 by means of a jacket or casing including casing section 1.4 which extend. from the front of the cylinder 1 around thesides to the back, as. shown in the drawings. On the air intake side at. the position of the arrows R (Figs. 1 and 3) the guiding casing sections 14 are open, or spaced apart, as distinguished from the usual closed off casing when a blower is used to impel air over air-cooled cylinders. As shown in Fig. 2, the air-guiding casing sections 14 on the respective sides ofthe cylinder and cylinder head terminate on the forward or anterior side of the cylinder in such a way as to leave free a broad air gap 15', directly in front of the cylinder 1. A still broader air gap. 15 is provided for the cylinder head 3, in accordance with which a greater mass of air may be drawn therethrough. The width of the air gaps 15 and 15' are preferably of such a magnitude as to leave the entire air intake side of the cylinder and cylinder head unobstructed.

On the opposite side of the cylinder and cylinder head from the air gaps 15 and 15', the guiding casing sections 14 terminate in the vicinity of the exhaust nozzle 13 in a surrounding portion 16, which in connection with the exhaust nozzle form an ejector. A mixing tube 17 is attached to the section 16, as shown in Figs. 1 and 3. The exhaust gases from the nozzle 13, together with the air mixed therewith, may be conducted from the mixing pipe 17 into a diffuser, not shown.

During the operation of the engine, the exhaust gases 3 flow directly through the exhaust gas conduit 12 in the cylinder head into the nozzle 13 and then into the mixing tube 17. Due to the ejector or suction action of the exhaust gases flowing from the nozzle 13, cooling air is aspirated in the direction of the arrows R through the air gaps 15 and 15', between the cooling ribs 4, 5, 6, 7 and 8 around the cylinder and cylinder head, substantially without change in direction, and is mixed with the exhaust gases in the mixing tube 17. In this operation the injection nozzle 11 and its seat including the walls of the conduit 11' are efiectively cooled.

It is to be understood that, while the invention has been described in connection with the engine illustrated in the drawings, the invention is not limited to a particular type of internal combustion engine. The cooling device in accordance with the invention, is applicable to diesel and Otto cycle engines which can be operated on the 2- or 4-cycle system. Furthermore, various cylinder head constructions may be used. The invention is also applicable to multi-cylinder air-cooled internal combustion engines.

This application includes subject matter disclosed in the applicants copending application Ser. No. 484,092, filed January 26, 1955.

We claim:

1. A cylinder for air-cooled internal combustion engines provided with a jacket for guiding cooling air thereover and with an exhaust gas ejector for impelling the cooling air over the cylinder, characterized in that the jacket is open on the side of the cylinder and its cylinder head opposite that of the ejector permitting unrestricted access of cooling air directly to the cylinder and cylinder head, a fuel injection nozzle or spark plug, as the case may be, on the nnjacketed side of the cylinder head and directly exposed to the incoming cooling air drawn across the cylinder head by the ejector, and exhaust gas conduit in the cylinder head, and in that the ejector includes a single exhaust gas ejector nozzle forming a direct, substantially straight line continuation of said exhaust gas conduit, and an air flow pipe connected into said jacket and surrounding the discharge end of said ejector nozzle, said ejector nozzle being spaced substantially centrally with respect to the air flow through said air-flow pipe, said ejector nozzle extending from the cylinder head on the side directly opposite that of the open side of the jacket in a direction directly away from the cylinder head so as to eject air through said air flow pipe and to draw the cooling air through the opening in the jacket and over the cylinder and cylinder head without appreciable change in the direction of fiow.

2. A cylinder as claimed in claim 1, in which the ejector nozzle is integral with the cylinder head.

3. A cylinder as claimed in claim 1, including an exhaust gas conduit integral with the cylinder head and ejector nozzle.

4. A cylinder as claimed in claim 1, including horizontal cooling ribs on the cylinder and cylinder head, and in which the jacket comprises a casing of sheet material having edges spaced apart on its open side providing an unobstructed gap the width of which at the position of the cylinder head is such that the cooling ribs of the cylinder head are not appreciably covered, and the width of the 4 gap at the position of the cylinder is such that the respective edges of the casing extend over the portions of the cooling ribs on the respective sides of the cylinder to an extent at least to almost cover or mask said portions of the ribs.

5. In an air-cooled internal combustion engine including at least one cylinder having a cylinder head, a casing of sheet material for guiding cooling air over the cylinder and cylinder head having spaced edges on one side of the cylinder and cylinder head defining an opening permitting access of cooling air directly to the cylinder and cylinder head, and an ejector including a single ejector nozzle located on the side of the cylinder and cylinder head opposite said opening, the improvement in which the ejector includes means connected with said casing forming an annular air-flow passageway surrounding the discharge end of said nozzle and said nozzle projects from the side of the cylinder head substantially centrally into said air-flow passageway and is arranged to deliver exhaust gases from the cylinder head in a direction away from the cylinder head to eject air through said annular air-flow passageway and to draw cooling air through said opening in the casing and over the cylinder and cylinder head without appreciable change in its direction of flow.

6. An air-cooled internal combustion engine as claimed in claim 5, including horizontal cooling ribs on the sides of the cylinder head, the spaced edges of the casing on the opposite sides of the opening at the position of the cylinder head being spaced apart a distance such that the cooling ribs of the cylinder head are not appreciably masked at the opposite sides of the opening.

7. An air-cooled internal combustion engine as claimed in claim 6, including cooling ribs on the top of the cylinder head extending in the direction of the flow of cooling arr.

8. In an air-cooled internal combustion engine including at least one cylinder having a cylinder head, a casing of sheet material for guiding cooling air over the cylinder and cylinder head having spaced edges on one side of the cylinder and cylinder head defining an opening permitting access of cooling air directly to the cylinder and cylinder head, and an ejector located on the side of the cylinder and cylinder head opposite said opening, the improvement in which the ejector comprises means connected with said casing forming an air-flow passageway extending in a direction away from the cylinder head of the engine, said cylinder head being provided with an exhaust gas conduit leading directly to the side of the cylinder head toward said air-flow passageway, and a single exhaust gas ejector nozzle integral with the cylinder head of the engine extending axially into said air-flow passageway in spaced relation to the wall thereof and constituting a substantially straight line continuation of said exhaust gas conduit.

References Cited in the file of this patent UNITED STATES PATENTS 2,270,546 Neuland I an. 20, 1942 FOREIGN PATENTS 5,422 Great Britain Mar. 5, 1904 

